Benzene- and pyridine-incorporated octaphyrins with different coordination modes toward two Pd<sup>II</sup> centers.

Liu, Le; Hu, Zhiwen; Zhang, Fenni; Liu, Yang; Xu, Ling; Zhou, Mingbo; Tanaka, Takayuki; Osuka, Atsuhiro et al. · Nat Commun · 2020

basic_science · Level V

Where this comes from

Abstract

Expanded porphyrins have received considerable attention due to their unique optical, electrochemical and coordination properties. Here, we report benzene- and pyridine-incorporated octaphyrins(1.1.0.0.1.1.0.0), which are synthesized through Suzuki-Miyaura coupling of α,α'-diboryltripyrrane with m-dibromobenzene and 2,6-dibromopyridine, respectively, and subsequent oxidation with 2,3-dicyano-5,6-dichlorobenzoquinone. Both octaphyrins are nonaromatic and take on dumbbell structures. Upon treatment with Pd(OOCCH<sub>3</sub>)<sub>2</sub>, the benzene-incorporated one gives a C<sub>i</sub> symmetric NNNC coordinated bis-Pd<sup>II</sup> complex but the pyridine incorporated one gives C<sub>i</sub> and C<sub>s</sub> symmetric NNNC coordinated bis-Pd<sup>II</sup> complexes along with an NNNN coordinated bis-Pd<sup>II</sup> complex bearing a transannular C-C bond between the pyrrole α-positions. In addition, these two pyridine-containing NNNC Pd<sup>II</sup> complexes undergo trifluoroacetic acid-induced clean interconversion.